Elevated view of the side entrance of the U.S. Embassy in the Turkish capital, Ankara, after a suspected suicide bomber detonated an explosive device, Friday Feb. 1, 2013. The bomb appeared to have exploded inside the security checkpoint at the entrance of the visa section of the embassy. A police official said at least two people are dead.(AP Photo)— AP

Elevated view of the side entrance of the U.S. Embassy in the Turkish capital, Ankara, after a suspected suicide bomber detonated an explosive device, Friday Feb. 1, 2013. The bomb appeared to have exploded inside the security checkpoint at the entrance of the visa section of the embassy. A police official said at least two people are dead.(AP Photo)
/ AP

Emergency personnel are seen in front of a side entrance of the U.S. Embassy in the Turkish capital, Ankara, after a suspected suicide bomber detonated an explosive device, Friday Feb. 1, 2013. The bomb appeared to have exploded inside the security checkpoint at the entrance of the visa section of the embassy. A police official said at least two people are dead. (AP Photo/Burhan Ozbilici)— AP

Emergency personnel are seen in front of a side entrance of the U.S. Embassy in the Turkish capital, Ankara, after a suspected suicide bomber detonated an explosive device, Friday Feb. 1, 2013. The bomb appeared to have exploded inside the security checkpoint at the entrance of the visa section of the embassy. A police official said at least two people are dead. (AP Photo/Burhan Ozbilici)
/ AP

FILE - In this April 14, 2012 file photo, Didem Tuncay, then a diplomatic reporter for Turkish news channel NTV, interviews Iran's Chief nuclear negotiator Saeed Jalili in Istanbul, Turkey. Tuncay, a respected television journalist, 38, was injured after a suicide bomber detonated an explosive device at the entrance of the U.S. Embassy in the Turkish capital, Ankara, Turkey, Friday, Feb. 1, 2013, A hospital official said she was " not in a critical conditoion." (AP Photo/Burhan Ozbilici, File)— AP

FILE - In this April 14, 2012 file photo, Didem Tuncay, then a diplomatic reporter for Turkish news channel NTV, interviews Iran's Chief nuclear negotiator Saeed Jalili in Istanbul, Turkey. Tuncay, a respected television journalist, 38, was injured after a suicide bomber detonated an explosive device at the entrance of the U.S. Embassy in the Turkish capital, Ankara, Turkey, Friday, Feb. 1, 2013, A hospital official said she was " not in a critical conditoion." (AP Photo/Burhan Ozbilici, File)
/ AP

Medics and firefighters carry an injured woman on a stretcher to an ambulances after a suicide bomber had detonated an explosive device at the entrance of the U.S. Embassy in the Turkish capital, Ankara, Turkey, Friday, Feb. 1, 2013. A suspected suicide bomber detonated an explosive device at the entrance of the U.S. Embassy in the Turkish capital on Friday, killing himself and one other person, officials said. (AP Photo/Burhan Ozbilici)— AP

Medics and firefighters carry an injured woman on a stretcher to an ambulances after a suicide bomber had detonated an explosive device at the entrance of the U.S. Embassy in the Turkish capital, Ankara, Turkey, Friday, Feb. 1, 2013. A suspected suicide bomber detonated an explosive device at the entrance of the U.S. Embassy in the Turkish capital on Friday, killing himself and one other person, officials said. (AP Photo/Burhan Ozbilici)
/ AP

ANKARA, Turkey 
The suicide bomber who struck the U.S. Embassy in Ankara spent several years in prison on terrorism charges but was released on probation after being diagnosed with a hunger strike-related brain disorder, officials said Saturday.

The bomber, identified as 40-year-old leftist militant Ecevit Sanli, killed himself and a Turkish security guard on Friday, in what U.S. officials said was a terrorist attack. Sanli was armed with enough TNT to blow up a two-story building and also detonated a hand grenade, officials said.

Turkish Prime Minister Recep Tayyip Erdogan said Friday that police believe the bomber was connected his nation's outlawed leftist militant group Revolutionary People's Liberation Party-Front, or DHKP-C. And on Saturday DHKP-C claimed responsibility for the attack in a statement posted on a website linked to the group. It said Sanli carried out the act of "self-sacrifice" on behalf of the group.

The group called itself "immortal" and said, "Down with imperialism and the collaborating oligarchy." But it gave no reason for attacking the U.S. Embassy. The authenticity of the website was confirmed by a government terrorism expert who spoke on condition of anonymity in line with rules that bar government employees from speaking to reporters without prior authorization.

Turkey's private NTV television, meanwhile, said police detained three people on Saturday who may be connected to the U.S. Embassy attack during operations in Ankara and Istanbul. Two of the suspects were being questioned by police in Ankara, while the third was taken into custody in Istanbul and was being brought to Ankara.

NTV, citing unidentified security sources, said one of the suspects is a man whose identity Sanli allegedly used to enter Turkey illegally, while the second was suspected of forging identity papers. There was no information about the third suspect.

Earlier, Turkish Interior Minister Muammer Guler said Sanli had fled Turkey after he was released from jail in 2001, but managed to return to the country "illegally," using a fake ID. It was not clear how long before the attack he had returned to Turkey.

NTV said he is believed to have come to Turkey from Germany, crossing into Turkey from Greece. Police officials in Ankara could not immediately be reached for comment.

DHKP-C has claimed responsibility for assassinations and bombings since the 1970s, but it has been relatively quiet in recent years. Compared to al-Qaida, it has not been seen as a strong terrorist threat.

Sanli's motives remained unclear. But some Turkish government officials have linked the attack to the arrest last month of dozens of suspected members of the DHKP-C group in a nationwide sweep.

Speculation also has abounded that the bombing was related to the perceived support of the U.S. for Turkey's harsh criticism of the regime in Syria, whose brutal civil war has forced tens of thousands of Syrian refugees to seek shelter in Turkey. But Prime Minister Erdogan has denied that.

Officials said Sanli was arrested in 1997 for alleged involvement in attacks on Istanbul's police headquarters and a military guesthouse, and jailed on charges of membership in the DHKP-C group.